Somewhat similar, I was at costco and they were out. The cell phone kiosk in Costco was busy and they have a running list of people waiting. It can't hurt to try Sams club but I wouldn't hold your breath.
I purchased a silver 6+ 16gb from Sam's last week. There was no line and it took about 20 minutes to complete.
A few caveats about buying from Sam's:
-They only carry the 16gb storage level of the phone
-They don't sell phones at off contract prices for the first couple of months a phone is out
So I had to sign up for a Verizon contract in order to get the phone. I got home, swapped out my AT&T sim, and it worked fine. Now I'm just waiting for the first bill from Verizon to arrive and I'll cancel the service and pay the fees.